Blood corpuscles are present and the respiratory pigment is present inside the blood

Advantages of closed circulatory system

The closed circulatory system is more efficient.

Since blood circulates only inside blood vessels it can do it with more pressure reaching farther distances between the organs.

The circulatory speed also increases making it possible for more oxygen supply to great consuming tissues, like the muscle tissues that then can perform faster movements.

HUMAN HEART

LOCATION

The heart is a hollow, cone-shaped structure located between the lungs and behind the sternum (breastbone).

Two-thirds of the heart is located to the left of the midline of the body and 1/3 is to the right.The apex (pointed end) points down and to the left.

It is 5 inches (12 cm) long, 3.5 inches (8-9 cm) wide and 2.5 inches (6 cm) from front to back, and is roughly the size of your fist.

HEART:EXTERNAL STRUCTURE

External view of human heart

The heart has four chambers-

Two auricles or atria

Two ventricles

The auricles are demarcated from the ventricles by a groove called coronary sulcus or atrioventricular groove.The two ventricles are demarcated by an oblique groove called the interventricular sulci.

Layers of the heart and Pericardium

The heart wall has three tissue layers. These are as follows:Innermost layer- The endocardium is a thin, smooth layer of epithelial cells that lines the heart’s interior. The endocardium provides a smooth surface for easy flow as blood travels through the heart. Extensions of this membrane cover the flaps (cusps) of the heart valves.Middle layer-The myocardium, the heart muscle, is the thickest layer and pumps blood through the vessels. Outer layerThe epicardium is a serous membrane that forms the thin, outermost layer of the heart wall.

The pericardium is the sac that encloses the heart. The outermost and heaviest layer of this sac is the fibrous pericardium. Anatomically, the outer layer of this serous membrane is called the parietal layer, and the inner layer is the visceral layer, also known as the epicardium, as previously noted. A thin film of fluid between these two layers reduces friction as the heart moves within the pericardium.

HEART: INTERNAL STRUCTURE

The Heart is divided into separate right and left sections. Each of these (right and left) sections is also divided into upper and lower compartments known as atria and ventricles, respectively.

The auricles have thin walls - they pump blood into the ventricles that are just below them. The auricles are separated by inter-auricular septum.The septum show the presence of a depression -fossa ovalis. This is the remnant of the embryonic structure foramen ovale, which during the embryonic stages lead to passage of blood from right to left auricle.

The ventricles are lower chambers that are thick walled and separated by septum - the inter-ventricular septum. The left ventricle is larger and the walls are about three times thicker than the walls of the right ventricle. The left ventricle has to pump blood to into vessels that supply blood to entire body whereas the right ventricle has to pump it to the arteries that supply to the lungs.Internally the wall of the ventricles has a network of muscular ridges called columnae carneae or trabaculae carneae. there are also present muscular elevations called as the papillary muscles.

19. Chordae tendinae, 20. Trabaculae carneae, 23. Papillary muscles.

Valves- structure and function

Valves are flap-like structures that allow blood to flow in one direction (prevent the back flow of blood).

Aortic Semilunar Valve - prevents the back flow of blood as it is pumped from the left ventricle to the aorta.

Mitral Valve - prevents the back flow of blood as it is pumped from the left atrium to the left ventricle.

Pulmonary Semilunar Valve - prevents the back flow of blood as it is pumped from the right ventricle to the pulmonary artery.

Tricuspid Valve - prevents the back flow of blood as it is pumped from the right atrium to the right ventricle.

Papillary muscles -muscles in the ventricles connected to the chordae tendinae. These muscles help stabilize the AV valves during ventricular contraction.

CARDIAC MUSCLE

Cardiac muscle cells are uninucleate, somewhat striated cells, that contain lots of mitochondria and are interconnected branching fibers that are connected at specialized cell-to-cell junctions.These myocardial cells, called cardiomyocytes, have the characteristics of automaticity, conductivity, contractility and excitability.

Automaticity is a characteristic unique to cardiac muscle and refers to the heart's ability to generate its own signal to contract.

Conductivity- Cardiac muscle has the ability to pass the electrical signal from one fiber to the next until it has spread throughout the entirety of the heart.

The heart's ability to respond to an additional stimulus and change its rate of contraction is known as excitability.

Contractility is the ability of the heart to generate tension, or produce force, in order to eject blood from the heart.

Conduction system of heart

An electrical impulse generated in one part of the heart spreads to the entire heart via the conduction system of the heart. Cardiac cells can generate electrical impulses (action potentials) without any input from the nervous system.

The conducting system of the heart consists of cardiac muscle cells and conducting fibers (not nervous tissue) that are specialized for initiating impulses and conducting them rapidly through the heart. They initiate the normal cardiac cycle and coordinate the contractions of cardiac chambers. Both atria contract together, as do the ventricles, but atrial contraction occurs first.The conducting system provides the heart its automatic rhythmic beat. For the heart to pump efficiently and the systemic and pulmonary circulations to operate in synchrony, the events in the cardiac cycle must be coordinated.

Working of the conducting system of heart

The normal heart begins with an electrical impulse from the SA (sinoatrial) node, located high in the right atrium. The SA node is the pacemaker of the normal heart, responsible for setting the rate and rhythm. The impulse spreads through the walls of the atria, causing them to contract. Next, the impulse moves through the AV (atrioventricular) node, into the conduction bundles which are located in the ventricles themselves. These are bundles of His, that further branch to form Purkinje fibers. As the impulse travels down the bundles to the purkinje fibers, the ventricles contract. The cycle then repeats itself.

Types of circulation

There are two main types of circulation-

Systemic circulationThe blood flows from the left ventricle, through various parts of the body, to the right atrium. This circulation is responsible for keeping the body tissues alive by supplying a continuous stream of blood to them.

Pulmonary circulationThe blood flows from the right ventricle, through the lungs, to the left atrium. This circulation is responsible for oxygenation of blood. Thus, the pulmonary circulation makes sure that systemic circulation remains effective.

Portal circulationIt is a part of systemic circulation, which has the following characteristics.

The blood passes through two sets of capillaries before draining into a systemic vein.

The vein draining the first capillary network is known as portal vein which branches like an artery to form the second set of capillaries or sinusoids. Examples: hepatic portal circulation, hypothalamo hypophyseal portal circulation and renal portal circulation.

Coronary circulation,It is a part of the systemic circulatory system that supplies blood to and provides drainage from the tissues of the heart. Coronary arteries arise from the aorta just beyond the semilunar valves; during diastole, the increased aortic pressure above the valves forces blood into the coronary arteries and thence into the musculature of the heart. Deoxygenated blood is returned to the chambers of the heart via coronary veins; most of these converge to form the coronary venous sinus, which drains into the right ventricle below the tricuspid valve.

single circulation

double circulation

Cardiac cycle

The cardiac cycle is the sequence of events that occurs during one heart beat. Thus, one cardiac cycle is completed when the heart fills with blood and the blood is pumped out of the heart.

Joint diastole

Both atria and ventricles are relaxed

Right atrium receives blood from vena cavae

Left atrium receives blood from pulmonary veins

Some blood flows directly into the ventricles

lasts for 0.4 sec.

Atrial systole

Atria contract.

Blood is forced into the ventricles.

The Atrioventricular valves are open.

Lasts for 0.1 sec.

Atrial diastole

Atrial relax

blood flows into the atrium.

lasts for 0.7 sec

Ventricular systole

Ventricles contract

high pressure in ventricles

Blood flows from left ventricle into the aortic arch, and from right ventricle into the pulmonary arch

Bicuspid and tricuspid valves close, producing a loud‘LUB’ sound

lasts for 0.3 sec

Ventricular diastole

Ventricles relax

Drop in blood pressure in ventricles causes semi-lunar valves in the arches to close

Myogenic heart

Cardiac impulse originates in the heart itself at a patch of modified heart muscles.

Impulse spreads over the heart via modified cardiac muscles.

Heart removed from the body will continue to beat if given nourishment and proper conditions.

Found in molluscs and vertebrates.

Heart rate and Pulse

One systole and one diastole makes one complete heart beat which lasts for about 0.8 sec.The heart rate of healthy adult is 70 -75/ min. Pulse is the wave of distention that can be felt at certain points in the arteries.Each heart beat sends down one pulse along the arteries.

Refractory period: Property of cardiac muscle– once it has begun to contract it does not respond to any other stimulus until it begins to relax.

Cardiac output: The amount of blood flowing from the heart over a period of time. i.e.. The amount of blood expelled from the heart in one minute.

Cardiac reserve: Ratio between the max. cardiac output a person can achieve and the cardiac output at rest.

Blood pressure

The lateral pressure of the blood exerted on the wall of the blood vessel. During peak ventricular contraction the pressure reaches max.—SYSTOLIC BLOOD PRESSURE (SBP) During relaxation of the ventricle the pressure reaches a min. just before the start of the next contraction.– DIASTOLIC BLOOD PRESSURE (DBP) The normal BP is 120/80mm of Hg Blood pressure is determined by an instrument SPHYGMOMANOMETER.

Adaptation:Thin/ single celled permit diffusion/ exchange of food/ gases and waste products between blood and protoplasm of cells.

Competitive focus: Arterial system and venous system

BLOOD

Blood is red coloured fluid that flows through the vessels. It is alkaline in nature and is a complex transport medium.The oxygenated blood is bright red and the deoxygenated blood is purple coloured.Blood consists of Plasma – straw coloured fluid.Formed elements– blood cells or corpuscles

Blood plasma

It is a straw coloured fluid, and forms 60% of the blood.It contains- Water (85-90%) and Inorganic ions (0.9%)Organic compounds present are

Competitive focus: Haemoglobin and anaemia

Types of anemia1. Iron deficiency anaemia-Cause- insuffiecient dietary intake or absorption of iron. Due to this hb cannot be formed.2. Sickle cell anemia- Genetic disease Leading to Sickle-shaped RBC3. Thalassemia- Genetic disease Produce abnormal hb molecule RBC- small and fragile4.Pernicious anemia Autoimmune disease Vit B12 cannot be absorbed due to lack of intrinsic factor.Thus due to less Vit B12, hb cannot be produced.5. Aplastic anemia Inability of bone marrow to produce RBC6. Microcytic, hypochromic anemia Due to chronic blood loss, iron is not absorbed in sufficient amounts from the intestine to form hb RBC becomes smaller than the normal and have too little hb.7. Megaloblastic anemia Loss of Vit B12, folic acid and intrinsic factor from stomach mucosa, leads to slow production of erythroblasts in the bone marrow. RBC- grow too large, with odd shapes These RBC have fragile membranes and rupture easily.

Leucocytes or White Blood Cells: It is rounded, irregular or amoeboid.They lack haemoglobin. 4000 – 8000 per mm3 of blood.They are nucleated and show diapedesis.Agranulocytes include Monocyte-ingest microorganismsLymphocyte—produce antibodiesGranulocytes include Eosinophil– engulf particlesBasophil– contain serotoninNeutrophil– show phagocytosis

Thrombocytes or platelets: These are small, oval, rounded or biconvex disc shaped bodies. They are colourless without nucleus. They play an important role in blood clotting.

Blood groups

The ABO Blood Group SystemAustrian-American immunologist and pathologist Karl Landsteiner discovered human blood groups. Karl Landsteiner's work made it possible to determine blood groups and thus paved the way for blood transfusions to be carried out safely. For this discovery he was awarded the Nobel Prize in Physiology or Medicine in 1930.

At times, it was observed that mixing blood from two individuals lef to blood clumping or agglutination. Later it was understood that the agglutinated red cells can clog blood vessels and stop the circulation of the blood to various parts of the body. The agglutinated red blood cells also crack and their contents leak out in the body. The RBCs contain haemoglobin which becomes toxic when outside the cell. This must have been the phenomena that occurred in the blood transfusion cases that ended up with fatality of the patient at the receiving end. Karl Landsteiner discovered that blood clumping was an immunological reaction which occurs when the receiver of a blood transfusion has antibodies against the donor blood cells! People learned that, compatibility of blood groups needed to be checked before anything else was done. If they are not, the red blood cells from the donated blood will agglutinate. This can have fatal consequences for the patient. There are four major blood groups determined by the presence or absence of two antigens – A and B – on the surface of red blood cells:

Group A – has only the A antigen on red cells (and B antibody in the plasma)

Group B – has only the B antigen on red cells (and A antibody in the plasma)

Group AB – has both A and B antigens on red cells (but neither A nor B antibody in the plasma)

Group O – has neither A nor B antigens on red cells (but both A and B antibody are in the plasma)

Rh factor

Rh blood types were discovered in 1940 by Karl Landsteiner and Alexander Wiener.

Approximately half of the children born to an Rh-negative mother and Rh-positive father will be Rh positive.Rh incompatibility usually isn't a problem if it's the mother's first pregnancy because, unless there's some sort of abnormality, the fetus's blood does not normally enter the mother's circulatory system during the course of the pregnancy.However, during delivery, the mother's and baby's blood can intermingle. If this happens, the mother's body recognizes the Rh protein as a foreign substance and can begin producing antibodies (protein molecules in the immune system that recognize, and later work to destroy, foreign substances) against the Rh proteins introduced into her blood.Other ways Rh-negative pregnant women can be exposed to the Rh protein that might cause antibody production include blood transfusions with Rh-positive blood, miscarriage, and ectopic pregnancy.Rh antibodies are harmless until the mother's second or later pregnancies. If she is ever carrying another Rh-positive child, her Rh antibodies will recognize the Rh proteins on the surface of the baby's blood cells as foreign, and pass into the baby's bloodstream and attack those cells. This can lead to swelling and rupture of the baby's RBCs. A baby's blood count can get dangerously low when this condition, known as hemolytic or Rh diseaseof the newborn, occurs.

Erythroblastosis fetalis

Erythroblastosis fetalis is a potentially life-threatening blood disorder in a fetus or newborn infant.Erythroblastosis fetalis develops in an unborn infant when the mother and baby have different blood types. The mother produces substances called antibodies that attack the developing baby's red blood cells.

BLOOD TYPING (click on the image to go to the link)

Blood clotting

The property of blood to change from the fluid state to a jelly state after coming out of the blood vessel. Platelets release two factors—serotonin and thromboplastin. Serotonin causes contraction of blood vessels that reduce blood loss. Blood contains thromboplastin, rupturing of platelets renders this active. Thromboplastin converts prothrombin to thrombin. Thrombin converts fibrinogen to fibrin Fibrin is insoluble and forms a mesh or network. This traps the RBC to form a clot.

Competitive focus: clotting factors

Coagulation factor - any of the factors in the blood whose actions are essential for blood coagulation Plasma protein - any of the proteins in blood plasmaFactor I, fibrinogen - a protein present in blood plasma; converts to fibrin when blood clotsFactor II, prothrombin - a protein in blood plasma that is the inactive precursor of thrombinFactor III, thrombokinase, thromboplastin - an enzyme liberated from blood platelets that converts prothrombin into thrombin as blood starts to clotCalcium ion, factor IV - ion of calcium; a factor in the clotting of bloodAccelerator factor, factor V, proaccelerin, prothrombin accelerator - a coagulation factorCothromboplastin, factor VII, proconvertin, stable factor - a coagulation factor formed in the kidney under the influence of vitamin K.Antihaemophilic factor, antihaemophilic globulin, antihemophilic factor, antihemophilic globulin, factor VIII, Hemofil - a coagulation factor (trade name Hemofil) whose absence is associated with hemophilia A.Christmas factor, factor IX - coagulation factor whose absence is associated with hemophilia B.Factor X, prothrombinase - coagulation factor that is converted to an enzyme that converts prothrombin to thrombin in a reaction that depends on calcium ions and other coagulation factorsFactor XI, plasma thromboplastin antecedent - coagulation factor whose deficiency results in a hemorrhagic tendency.Factor XII, Hageman factor - coagulation factor whose deficiency results in prolongation of clotting time of venous blood.Factor XIII, fibrinase - in the clotting of blood thrombin catalyzes factor XIII into its active form (fibrinase) which causes fibrin to form a stable clot.

Lymphatic system

The lymphatic system consists of a fluid (lymph), vessels that transport the lymph, and organs that contain lymphoid tissue. Lymph – is a clear fluid carrying protein, waste products, toxins, bacteriaLymph Nodes- act as filtering stations throughout the body removing the unwanted substances.Lymphatic organs are characterized by clusters of lymphocytes and other cells, such as macrophages, enmeshed in a framework of short, branching connective tissue fibers. The organs include- tonsils, spleen, thymus and lymph nodes.

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